refactor(verification): externalize verification dependencies [part 2/2]

[glevco]

Depends on #859

Motivation

Finish the refactor started in #859 (read its description for more info). After this PR, all verification dependencies are externalized and pre-calculated.

Acceptance Criteria

• Add missing verification dependencies for transactions: token info and best block tips.
• Add new auxiliary methods to SimpleMemoryStorage.
• Update verifiers and VerificationService accordingly.
• Update Transaction methods related to token info to receive an optional SimpleMemoryStorage, which may be used to retrieve data.

Checklist

• If you are requesting a merge into master, confirm this code is production-ready and can be included in future releases as soon as it gets merged

[codecov]

Codecov Report

Attention: Patch coverage is 98.01980% with 4 lines in your changes are missing coverage. Please review.

❗ No coverage uploaded for pull request base (refactor/verification-dependencies@6578961). Click here to learn what that means.

❗ Current head 2bdaa2a differs from pull request most recent head 74b1849. Consider uploading reports for the commit 74b1849 to get more accurate results

Files	Patch %	Lines
...athor/transaction/storage/simple_memory_storage.py	94.64%	3 Missing ⚠️
hathor/verification/block_verifier.py	90.90%	1 Missing ⚠️

Additional details and impacted files

@@                          Coverage Diff                          @@
##             refactor/verification-dependencies     #904   +/-   ##
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  Lines                                         ?    22508           
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  Hits                                          ?    19219           
  Misses                                        ?     2618           
  Partials                                      ?      671           

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[msbrogli]

Have you had this exception raised? I mean, this condition would be impossible if the transaction has been validated.

No problem with this change. Just checking if this condition occurred with you.

[glevco]

It's just that before, this method was only called during verification. Now, it's called before verification (when retrieving the verification dependencies). So, if the tx is invalid, it will raise this exception during that retrieval.

[msbrogli]

It seems like we are juggling to make the new memory storage work alongside the current code. I think we can spawn an ephemeral verifier that carries a storage and use it to run the verification. It can be either set to tx.storage or to any other storage. What do you think?

[glevco]

Indeed, this was not a good solution. I have solved this using a StorageProtocol, so both TransacionStorage and SimpleMemoryStorage have an unified interface that can be received by those methods. It was implemented in #922, and after it's merged to master I'll rebase this PR so this is updated.

[glevco]

Moved to PRs #1022 and #1023.